Depends on what you are trying to achieve because if you blur everything it looks like you took a photo while the phone was falling out of your hand. You should use the relative camera to stay fixed to the truck and take a pic while it's moving to get motion blur. Or you can use reshade
i make them blured with a site, and the site i use doesnt have the ability to unblur the places i want (for example the body of the truck), and so, the only way is to blur the whole thing.
You should get paint.net. Really powerful image editor. There are also more ways to have motion blur in your beamng images so just look up beamng motion blur screenshot
No. Reshade is something you install into BeamNG. Try looking up both and see how they work to not derail this thread any more